There are known in the prior art various forms of breathing sytems which provide filtered air to a wearer for breathing. Typically, air is drawn into an enclosed oral-nasal cavity through a filter by the action of inhalation, and air flow is controlled so as to prevent fogging of the lenses or goggles which often form part of the system. While these systems are generally satisfactory, it is desirable to have a system which is set up to prevent the infiltration of chemical or biological elements and to provide for cooling of the head of the wearer.